DESCRIPTION The mesolimbic projection from the ventral tegmental area (VTA) to the nucleus accumbens (NAc) is a fundamental component of the neural circuit underlying reward and reinforcement, including drug-seeking behavior. This research focuses on the interaction of acetylcholine (ACh) and GABA in this pathway in relation to cocaine. The goal of the proposed fellowship is to test the hypothesis that cocaine exposure decreases the inhibitory impact of GABA on ACh activity of GABA on ACh activity in the NAc. Two experiments will use microdialysis for ACh in the NAC combined with microinfusions of GABA agonists and antagonists in the VTA and NAc of rats that have self-administered cocaine. Results will be compared to data from animals that receive passive (i.e. yoked) cocaine exposure and drug naive rats. The results from these studies will provide additional information into the GABA-ACh injection between the VTA and NAc and contribute to our understanding of how the neurochemical dynamics of the mesolimbic system are altered by the psychostimulant exposure.